1. Field of the Invention
The present invention relates to a dial mechanism incorporated into a camera. More particularly, the present invention relates to a double dial mechanism in which two dials to be rotated independently from one another during operation are coaxially arranged.
2. Description of the Related Art
In general, cameras are provided with various setting buttons and setting dials for setting photographic and other conditions. In recently developed electronic cameras, a setting system is adopted in which photographic conditions are set using setting buttons. In these systems, the photographic conditions are set while a photographer is looking at marks and numerical values displayed on a display section of the camera, and thus the setting operation is complicated.
In setting dial systems, it is possible to conduct setting only when a rotational position of the setting dial is set at a predetermined position. The setting can be easily conducted. However, from the viewpoint of human engineering, in order to ensure proper operation, a diameter of the dial can not be reduced too much. Accordingly, it is difficult to ensure a space for arranging a plurality of setting dials in the camera body, and the setting dials obstruct the miniaturization of cameras. In order to solve the above problems, there has conventionally been proposed a dial mechanism in which two setting dials are coaxially arranged.
FIGS. 4A and 4B are respectively a cross-sectional view and a schematic plan view showing an example of an arrangement of a primary portion of the dial mechanism. In a portion of the camera body, in this case, on an ornamental plate 101 of a top body panel of the camera body, there is integrally provided a cylindrical boss 111 that protrudes from the ornamental plate 101. Into this cylindrical boss 111, a shaft portion 131 of a shutter dial 103 having a short cylindrical dial knob 132 is inserted. A shutter code plate 133 is fixedly attached to an inner end portion of this shaft portion 131. On a surface of this shutter code plate 133, there is provided a conductor pattern 134 for a shutter composed of a conductive film having a predetermined pattern. A conductive shutter brush 136 attached to a circuit board 102, which is supported by and fixed to the ornamental plate 101, slides on this conductor pattern 134 for controlling the shutter. In this way, the shutter rotation detecting mechanism is composed. When the above shutter dial 103 is rotated during operation, a contact position of the shutter brush 136 with the conductor pattern 134 for controlling the shutter on the shutter code plate 133, which is rotated integrally with the shutter dial 103, is changed. Therefore, a rotational position of the shutter dial 103 is detected as a code value, and a shutter speed is set to correspond with the rotational position of the shutter dial 103.
A disk-shaped photometry dial 104 is rotatably engaged with an outer circumference of the cylindrical boss 111. A protrusion 141 arranged in one portion of the circumference on the reverse side of the photometry dial 104 penetrates an arcuate opening groove 112 formed on the ornamental plate 101 and protrudes inside the ornamental plate 101. A photometry brush 146 is fixedly attached to a forward end of this protrusion 141. This photometry brush 146 is capable of sliding on a photometry conductor pattern 144 on the photometry code plate 143 formed in one portion of the circuit board 102. In this way, the photometry rotational position detecting mechanism is composed. When this photometry dial 104 is rotated during operation, the photometry brush 146 rotated integrally with the photometry dial 104 slides on the photometry conductor pattern 144, so that the contact position is changed, and a rotational position of the photometry dial is detected as a code value. In this way, a photometry condition is set to correspond with the rotational position.
In the above conventional double dial mechanism, the shutter dial 103 and the photometry dial 104 are arranged on the same axis. Accordingly, it is possible to incorporate the two dials in the camera body without using additional space on the camera body. Due to the foregoing, it is possible to miniaturize the camera without deteriorating the operation properties of the dial. However, the code plates 133, 143, respectively composing the rotational position detecting mechanisms for the shutter and photometry and the brushes 136, 146 are arranged on substantially the same plane. Therefore, in order to prevent the interference between each of the code plates 133, 143 and brushes 136, 146, it is necessary to arrange them at different positions in the radial direction. As a result, a space occupied by the rotational position detecting mechanism is increased. For the above reasons, even if the above double dial mechanism is adopted for the purpose of reducing space, miniaturization can not be sufficiently accomplished.
In the above conventional double dial mechanism, the photometry brush 146 arranged inside the ornamental plate 101 is slid on the code plate 143 for photometry. Therefore, it is necessary to form in the ornamental plate 101 an arcuate opening groove 112 into which a protrusion 141 of the photometry dial 104 is inserted. Since water can enter the camera body from this opening groove 112, not only is the water proofing property of the photometry brush 146 deteriorated, but so is the water proofing property of the entire camera. To make matters worse, when the opening groove 112 is formed, the mechanical strength in this region of the camera body is decreased. Since there are water proofing and mechanical strength problems as described above, an arc length of the opening groove 112 is necessarily restricted. As a result, a rotational angel of the photometry dial is also restricted, and it becomes difficult to ensure a rotational angle required for changing the photometry condition.